Pesticide and a process for its manufacture

ABSTRACT

Pesticidal compositions comprise water-decomposable compounds, adapted to generate toxic gases upon contact with water, held on a porous, fibrous carrier material.

ite States Rausclier et a1.

[ PESTICIDE AND A PROCESS FOR ITS MANUFACTURE [76] Inventors: HerbertRauscher, 1m Uhug 54; Werner Schoom, Bergerstrasse 342, both ofFrankfurt am Main, Germany [22] Filed: Feb. 5, 1970 [21] App1.No.: 9,073

[30] Foreign Application Priority Data Jan. 22, 1970 Germany ..P 20 02655.5

Feb. 8, 1969 Germany ..P 19 06 413.2

[52] US. Cl. ..424/27, 21/59, 2,1/108, 21/129, 43/125, 43/131, 424/128,424/129 [51] Int. Cl. ..A0lm l/20 [58] Field of Search ....424/27, 40,128, 129; 43/125, 43/131; 21/59, 108, 129

[56] References Cited UNITED STATES PATENTS 3,003,911 10/1961 Lindstromet a1. ..162/100 Stevens ..424/40 X 2,929,761 3/1960 2,519,045 8/1950Houghton ..424/129 X 2,112,624 3/1938 Houghton ..424/129 X 2,087,3687/1937 Wilson et a1 ..424/129 X 1,991,938 2/1935 Houghton ..424/129 X1,967,290 7/1934 Cooper ..424/40 X 1,818,136 8/1931 Houghton ..424/129 X1,704,607 3/1929 Houghton ..424/129 X 1,663,082 3/1928 Houghton..424/129 X FOREIGN PATENTS OR APPLICATIONS 338,408 2/ 1933 GreatBritain 407,792 3/1934 Great Britain 858,592 10/1952 Germany PrimaryExaminer-Shep K. Rose Attorney-Gordon W. Hueschen and TalivaldisCepuritis [5 7 ABSTRACT Pesticidal compositions comprisewater-decomposable compounds, adapted to generate toxic gases uponcontact with water, held on a porous, fibrous carrier material.

7 Claims, No Drawings PESTICIDE AND A PROCESS FOR ITS MANUFACTUREBACKGROUND OF THE INVENTION The present invention relates to a pesticidefrom which gaseous, toxic substances can be generated by the action ofwater or water vapor on finely distributed, decomposable compounds.

It is known to use pesticides in the form of readily decomposablecyanides or alkaline earth phosphides or earth metal phosphides which,under the action of water or water vapor, generate hydrogen cyanide orhydrogen phosphide as gaseous, toxic substances. In practice,difficulties are involved in the use of such products. Thegas-generating compounds have to be brought into a form which preventsgas from being generated too rapidly and thus endangering the personusing the pesticide or even causing spontaneous combustion due to thelocalization of heat. Furthermore, this pesticide has to be such thatany residues, remaining after the decomposition and generation of theeffective substance, can be removed quantitatively, especially if theresidues themselves are toxic. To overcome these difficulties,gas-generating compounds such as calcium cyanide, aluminum phosphide,magnesium phosphide or calcium phosphide have been manufactured and usedin the form of tablets. Furthermore, such compounds have been coated ormixed with water-repellent substances such as paraffin in order tocontrol the rate at which gas is generated. The residues producedthereby are difficult to collect and remove. A process is also known inwhich the decomposable, gasgenerating compounds are enclosed in paperbags which are permeable to moisture but which repel water, so that therate at which gas is generated can be controlled indirectly. However,this is disadvantageous in that such bags permanently contain anaccumulation of the substances and, in the case of the incompletegenerating of gas, the incompletely decomposed residues constitute alatent danger due to their accumulation in the bags, for example if suchbags get into animal fodder or are accumulated in large quantities in aseparator where they can give rise to fires.

The object of the present invention is to provide a pesticide whichgenerates gas in a controllable manner, which is simple to dispose inthe space to be gassed and can be metered in a satisfactory manner,which virtually completely gasses out, and whose non-powdering residuesare subsequently easy to collect and remove.

SUMMARY OF THE INVENTION The present invention, which relates to theabovementioned pesticide from which gaseous, toxic substances aregenerated by the action of water or water vapor on finely distributed,decomposable compounds, is characterized in that the pesticide containsthe decomposable compounds together with a porous, shaped fibrousmaterial serving as a carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fibrous material containedin the pesticide of the present invention is advantageously in the formof textile fabrics, knitted fabrics, yarns, felts, fleeces, paper,

cardboard made from cellulose or materials containing cellulose, glassfibers, slag fibers, asbestos fibers, plastics material fibers,mechanical wood pulp, or two or more of these materials.

Advantageously, the finely distributed, decomposable compounds containedin the pesticide are substances which generate hydrogen phosphide and/orhydrogen cyanide. Such decomposable compounds are primarily calciumcyanide, magnesium phosphide, aluminum phosphide, or mixtures of two ormore of these substances. The decomposable compounds should be finelydistributed, the diameters of their particles being particularly between1 and 1,000 microns.

The pesticide can contain up to weight percent of the decomposablecompounds.

For many purposes, it is advisable for the pesticide to contain thedecomposable compounds mixed with a propellent. Such propellents areprimarily ammonium bicarbonate, sodium bicarbonate, ammonium carbamate,or mixtures of two or more of these substances.

To retard the gassing-out of the decomposable compounds, the particlesof these compounds may be coated with a water-repellent substance suchas synthetic resin, stearine, stearates, or hard paraffin.

In many cases, it is advantageous for the pesticide to contain a bindingagent for the fibrous material in order to improve the adhesion of thefibers. Urea may be used as such a binding agent. Alternatively,plastics materials such as polyvinyl chloride, polyurethane, polyester,or polystyrene are good binding agents for this purpose.

If required, the pesticide may also contain a foaming agent such asazodicarbonamide, and/or a softener for the binding agent.

According to the French Patent specification No. 1,531,677, it is known,inter alia, to embed metal phosphides in solid plastics material massesof polyesters, polyurethanes, polyvinyl chloride. However, thepesticides manufactured in this manner gas out so slowly that they areunsuitable for practical use. Furthermore, the structure of the plasticsmaterial loosens during gassing out, and powdered residues are produced.

The pesticide may also comprise two or more fiat structures, such asplates, webs, strips, or the like, which are connected to each other toform a so-called sandwich structure, the outer layers advantageouslycomprising the fibrous material without the decomposable compounds,since this virtually fully suppresses the powdering of the gassed-out,shaped bodies.

The porous fibrous material provided as an essential constituent of thepesticide serves to allow the atmosphere, and the moisture containedtherein, access to the separate particles of the decomposable compounds,so that controlled and virtually complete gassing-out can be effected.

The invention also relates to a process for manufacturing the pesticidedescribed. The process is characterized in that a suspension of thedecomposable compounds in an inert, volatile liquid which, if required,contains propellent, a water-repellent substance, a binding agent, afoaming agent, and a softener, is combined with the fibrous material,and the inert volatile liquid is removed by decanting and/or vaporizing.Advantageously, a white spirit, a low aliphatic alcohol, ortrichloroethylene may be used as the inert, volatile liquid.Alternatively, a suspension in a liquid, polymerizable mixture, whichpreferably forms polyesters or polyurethanes during polymerization, maybe used instead of the suspension in an inert, volatile liquid.

The process may be such that a preformed fibrous material, such as webs,plates, strips, parallelepipeds, balls, is impregnated or coated withthe suspension. If required, the suspension for coating the fibrousmaterial may contain a thickening agent such as finely distributedsilicon dioxide (aerosil) or cellulose fibers. Alternatively, however,the fibrous material may be finely distributed into the suspension andthe mixture thus obtained then shaped in a manner known per se.

In all cases, it is advisable to dry the fibrous material beforetreatment, so that any moisture contained therein cannot reactprematurely with the decomposable compound. Further, it is advantageousto carry out the process of the invention in an anhydrous environment.When carrying out this process, it must be ensured that all theadditives used are anhydrous and do not impair the porosity of thefibrous material.

In accordance with the process of the present invention, pesticides maybe manufactured which comprise two or more plates, webs, strips, or thelike, which are connected to each other.

The process for manufacturing the pesticides of the present inventionmay also be carried out continuously. For example, a web of the fibrousmaterial serving as the carrier may be manufactured continuously ordrawn from a supply roll, continuously coated or impregnated with thesuspension, continuously dried or gelled, arranged in layers with andconnected to one or a plurality of similar or different webs ifrequired, the finished end product then being cut into pieces of thedesired size, either by being stacked and combined to form packages, or,if required, coiled to form a roll perforated at specific intervals. Thefinished, shaped pesticide should be stored in air-tight containers fromwhich the desired quantities may be taken as required.

When the pesticide of the present invention is used, gassing-out iseffected by atmospheric moisture or, in certain forms of manufacture,water, penetrating through the fibrous material with the decompositionof the gas-generating compound embedded in the mass. The pesticide isloosened up to a certain extent by the gassing-out, although theconsistency of the shaped bodies is maintained to the extent where theymay readily be quantitatively collected and removed after the gassingoperation has been completed. This is particularly simple if thepesticide is produced in the form of plates or webs. Plates may beremoved from packaged stacks as required, and collected aftergassing-out. Optional lengths of webs may be drawn from rolls and rolledup again after gassing-out.

The pesticides manufactured in accordance with the invention may be usedfor gassing and disinfecting empty spaces, silos, warehouses and storesfor grain, tobacco, cocoa, coffee, or for similar purposes. The gaseoussubstances generated kill and exterminate insects, rodents, and otherpests.

EXAMPLE I A suspension of 224 parts by weight of aluminum phosphidehaving particle diameters between 5 and 600 microns, 50 parts by weightof polyvinyl chloride, and parts by weight of dioctylphthalate was madein 40 parts by weight of white spirit. A fibrous fleece of cellulosehaving a thickness of 0.2 mm and a weight of 46.5 g/m was coated on bothsides with this suspension to a thickness of 1 to 2 mm. The coatedfleece was heated for 20 minutes at 190 C.

When the pesticide was stored in air having percent relative humidity at20 C, 61.5 percent of the aluminum phosphide was decomposed to hydrogenphosphide after 24 hours, 88 percent after 48 hours, 96 percent after 72hours, and no undecomposed aluminum phosphide was detected after 7 days.

After gassing-out, the pesticide exhibited good solidity and did notpowder.

EXAMPLE 2 A suspension of 224 parts by weight of aluminum phosphidehaving particle diameters between 5 and 600 microns, 50 parts by weightof polyvinyl chloride, and 60 parts by weight of dioctylphthalate wasmade in 40 parts by weight of white spirit. A fibrous fleece ofcellulose having a thickness of 3 mm and a weight of 123 g/m was coatedon one side with this suspension to a thickness of 3 mm. The coatedfleece was heated for 20 minutes at 190 C.

When the pesticide was stored in air having a 85 percent relativehumidity at 20 C., 65 percent of the aluminum phosphide had decomposedto hydrogen phosphide after 24 hours, percent after 48 hours, 98 percent after 72 hours, and no undecomposed aluminum phosphide was detectedafter 7 days.

The pesticide exhibited good solidity after gassingout, and scarcelypowdered.

EXAMPLE 3 54 Parts by weight of aluminum phosphide having particlediameters between 5 and 600 microns, 46 parts by weight of cellulosefibers, and 2.5 parts by weight of polystyrene were suspended in 1,080parts by weight of trichloroethylene. The suspension was drawn offthrough a filter, and the residue was dried for 1 hour at 90 C. Theobtained disc-shaped body had a diameter of8 cm., a thickness of 16 mm,and a weight of 19.2 g.

When the body was stored in air having 85 percent relative humidity at20 C., 80.2 percent of the aluminum phosphide had decomposed to hydrogenphosphide after 24 hours, 93.9 percent after 48 hours, and

97.0 percent after 72 hours.

The shaped body had good solidity after gassing out.

EXAMPLE 4 169 Parts by weight of aluminum phosphide having particlediameters between 5 and 600 microns, 20 parts by weight of cellulosefibers, 50 parts by weight of polyvinyl chloride, and 60 parts by weightof dioctylphthalate were suspended in parts by weight of white spirit.The suspension was poured on to a glass plate to form a layer of 3 to 4mm thickness and was heated for 20 minutes at C. The layer was removedfrom the plate.

When the body was stored in air having 85 percent relative humidity at20 C., 72 percent of the aluminum phosphide had decomposed to hydrogenphosphide after 24 hours, 85 percent after 48 hours, and 95 percentafter 72 hours.

The shaped body had good solidity after gassing out, and powdered toonly a slight extent.

EXAMPLE 5 54 Parts by weight of 90 percent finely distributed calciumcyanide, 46 parts by weight of cellulose fibers, and 2.5 parts by weightof polystyrene were suspended in 1,080 parts by weight oftrichloroethylene. The suspension was drawn off through a filter, andthe residue was dried for one hour at 90 C. The discshaped body obtainedhad a diameter of 8 cm., a thickness of 16 mm, and a weight of 19 g.

Gassing out was virtually complete after 48 hours.

The shaped body was solid after gassing out, and free from dust.

EXAMPLE 6 54 Parts by weight of aluminum phosphide of the abovementioned granular size, and 46 parts by weight of cellulose fibers weresuspended in 900 parts by weight of methanol in which 2.5 parts byweight of urea had been dissolved. The suspension was drawn off througha filter, and the residue was dried for 1 hour at 60 C.

The gassing-out rate was the same as in Example 30 After gassing-out,the shaped body had the same very good solidity as before gassing-out,and did not powder.

EXAMPLE 7 The process was the same as in Example 3, with the exceptionthat finely distributed aluminum phosphide was used whose separateparticles were coated with a thin layer of hard paraffin.

The gassing-out rate was somewhat lower than in the case of thepesticide in Example 3. The gassed-out, shaped body had the same goodsolidity.

EXAMPLE 8 hydrous particles of decomposable toxic hydrogen cyanide orhydrogen phosphide gas-generating compounds finely distributed in saidporous web structure, said porous web structure serving to allow accessof moisture contained in the atmosphere to said finely distributedanhydrous particles of decomposable toxic hydrogen cyanide or anhydrousphosphide gas-generating compounds disposed therein with said polymericplastic adhesive binding agent by anhydrous impregnation and drying,said fibrous carrier being packaged in an air-tight and moisture-proofcontainer from which container desired metered quantities said fibrouscarrier may be taken as required to gas out and thereby kill insects,rodents, and other pests in confined empty spaces, said toxic gaseoussubstances being generated by penetration of atmospheric moisture intosaid fibrous carrier causing decomposition of said distributed toxicgas-generating compounds, said fibrous carrier being made of plural fiatstructured fibrous web strip outer layers connected to each other withpolymerized or polymerizable plastic adhesive binding agent to form asandwich porous web structure, and wherein said porous web structure iscut into pieces or coiled into a roll adapted to be perforated atspecific intervals in order to thereby provide desired quantities ofsaid fibrous carrier.

2. The toxic gas-generating pest exterminator in accordance with claim 1wherein a decomposable, toxic hydrogen cyanide gas-generating compoundis disposed in said porous web structure.

3. The toxic gas-generating pest exterminator in accordance with claim 2wherein the decomposable, toxic hydrogen gas-generating compound iscalcium cyanide.

4. The toxic gas-generating pest exterminator in accordance with claim 1wherein the decomposable, toxic hydrogen cyanide or hydrogen phosphidegasgenerating compound is a member of the group consisting of calciumcyanide, magnesium phosphide, aluminum phosphide, and mixtures thereof.

5. The toxic gas-generating pest exterminator in accordance with claim 1wherein the particle size of the decomposable compound contained in thepest exterminator is between 1 and 1,000 microns.

6. The toxic gas-generating pest exterminator in accordance with claim 1wherein the pest exterminator contains up to weight percent of thedecomposable compound.

7. The toxic gas-generating pest exterminator in accordance with claim 1wherein the binding agent is a member of the group consisting ofpolyvinyl chloride, polyurethane, polyester, polystyrene, and mixturesthereof.

1. A toxic gas-generating pest exterminator comprising a fibrous carrier having a porous web structure, and a polymeric plastic adhesive binding agent and anhydrous particles of decomposable toxic hydrogen cyanide or hydrogen phosphide gas-generating compounds finely distributed in said porous web structure, said porous web structure serving to allow access of moisture contained in the atmosphere to said finely distributed anhydrous particles of decomposable toxic hydrogen cyanide or anhydrous phosphide gas-generating compounds disposed therein with said polymeric plastic adhesive binding agent by anhydrous impregnation and drying, said fibrous carrier being packaged in an air-tight and moisture-proof container from which container desired metered quantities said fibrous carrier may be taken as required to gas out and thereby kill insects, rodents, and other pests in confined empty spaces, said toxic gaseous substances being generated by penetration of atmospheric moisture into said fibrous carrier causing decomposition of said distributed toxic gas-generating compounds, said fibrous carrier being made of plural flat structured fibrous web strip outer layers connected to each other with polymerized or polymerizable plastic adhesive binding agent to form a sandwich porous web structure, and wherein said porous web structure is cut into pieces or coiled into a roll adapted to be perforated at specific intervals in order to thereby provide desired quantities of said fibrous carrier.
 2. The toxic gas-generating pest exterminator in accordance with claim 1 wherein a decomposable, toxic hydrogen cyanide gas-generating compound is disposed in said porous web structure.
 3. The toxic gas-generating pest exterminator in accordance with claim 2 wherein the decomposable, toxic hydrogen gas-generating compound is calcium cyanide.
 4. The toxic gas-generating pest exterminator in accordance with claim 1 wherein the decomposable, toxic hydrogen cyanide or hydrogen phosphide gas-generating compound is a member of the group consisting of calcium cyanide, magnesium phosphide, aluminum phosphide, and mixtures thereof.
 5. The toxic gas-generating pest exterminator in accordance with claim 1 wherein the particle size of the decomposable compound contained in the pest exterminator is between 1 and 1,000 microns.
 6. The toxic gas-generating pest exterminator in accordance with claim 1 wherein the pest exterminator contains up to 70 weight percent of the decomposable compound. 